Drying and gas or vapor contact with solids – Apparatus – For diverse operations on treated material
Patent
1998-12-29
2000-09-05
Gravini, Stephen
Drying and gas or vapor contact with solids
Apparatus
For diverse operations on treated material
34 75, 34 79, 34211, 34212, F26B 1900
Patent
active
061124265
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention relates to a thermal compression plant with heat recovery for vacuum dryers as well as a drier incorporating the same plant.
With the words "thermal compression plant" it is meant a plant for the treatment of steams coming from products that have to be dried, preferably but not exclusively industrial leathers or similar products that must be treated at temperatures lower than that of evaporation at atmospheric pressure.
Vacuum dryers of the above mentioned type are known, for example, as described and claimed in the International patent application No. WO94/21828 and in the U.S. Pat. Nos. 3,027,651, and 3,303,574, all of which are incorporated herein by reference, having characteristics on which the initial part of the claim 1 is based.
In these known dryers at least one heated working table is provided, hermetically covered by a removable cover to define a drying chamber for products. The working table is heated by a first circuit for the circulation of a heating fluid, and the evaporation chamber is connected to a second circuit for the suction and condensation of the steam extracted from the products at a lower temperature than that of evaporation at atmospheric pressure.
The steam created in the drying chamber is conveyed in the working tables' side manifolds, in which are inserted tube nests condensers covered by a refrigerating fluid. To increase productivity, a high vacuum is provided in the evaporation chambers by means of vacuum pumps and/or blowers placed in series.
To maintain the condensation temperature at equilibrium, the working tables' condensers must be traversed by a refrigerating means at low temperature, for example chilled water which must be generated by specific chillers and kept in suitable tanks.
This part of the plant has initially a very high cost, it is not easily manageable, it has added maintenance costs and its energy consumption can be treble the consumption of the drier.
From French patent application No. 2,391,438 it is known a thermal plant for drying under vacuum products such as wood plates, which plant comprises a drying chamber, a first circuit for heating the drying chamber, a second circuit for suction and condensation of the steam generated by the products in the drying chamber. The first circuit includes a vacuum pump connected to a heat exchanger which has as chilling fluid the heating fluid circulating in the first circuit in order to recover the condensation heat and part of the energy furnished to the vacuum pump. The heat exchanger is in fluid communication with the outside and therefore has a working pressure equal to or higher than the atmospheric pressure, thereby affording very low condensation efficiency. Moreover, the vacuum pump operates on a mixture of water and oil and thus entails a very low suction efficiency, thereby maintaining in the drying chamber relatively high pressure and equilibrium temperature.
The main task of this invention is to eliminate the above mentioned inconveniences by making a thermal compression plant for vacuum dryers of industrial leathers and similar products which allows recovery of most of the energy for the functioning of the plant, which is highly reliable and of simple manufacture and which has a low initial cost as well as low management and maintenance.
A particular task is to eliminate the costly and complex condensers associated to the tables, as well as the very expensive chilling and accumulating plant of chilled water and moreover to recover most of the mechanical work carried out on the steam although maintaining the working temperatures relatively low.
These and other tasks, which will result more clearly further on, are achieved by a thermal compression plant with heat recovery in accordance with claim 1, which is characterised by the fact that the second steam circuit includes compression means which compress and superheat the steam to a higher temperature than the temperature of the working tables's heating fluid at continuous running, and at least a condenser having as ch
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Gravini Stephen
O"Byrne Daniel
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